Bush manufacturing method

Abstract

To provide a method for manufacturing a bushing that does not require strict dimensional accuracy when providing a resin layer on a core bar, and further, suppresses a generation of an excess resin layer that requires post-processing.SOLUTION: A method for manufacturing a bushing of the present invention for obtaining the bushing in which an inner member 4 having an outer peripheral surface F2 of a core grid 2 covered with a resin layer 3 is disposed inside an outer cylinder 6 via an elastic layer 5 includes: a resin tube preparation step for preparing a resin tube 13 made of resin as the resin layer 3; a core preparation step for preparing the core grid 2; a core heating step for heating the core grid 2; and a joining step in which the core grid 2 after the core heating step is inserted into the resin tube 13 through an opening A13 formed at an axial end 13a of the resin tube 13, thereby joining the core grid 2 and the resin tube 13.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bush. Background Art

[0002] As a conventional method for manufacturing a bush, which obtains a bush in which an inner member having an outer peripheral surface of a core metal covered with a resin layer is disposed inside an outer cylinder via an elastic layer, so-called insert molding is known, in which the resin layer is injection-molded using the core metal as an insert (see, for example, Patent Document 1). According to insert molding, after fitting the core metal into the mating surfaces of a mold, a resin material is injected into a cavity formed in the mating surfaces, whereby the core metal having the resin layer can be manufactured. Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Unexamined Patent Publication No. 2022-062999 Summary of Invention Problems to be Solved by the Invention

[0004] However, in the case of molding using a mold, it is necessary to increase the dimensional accuracy of each of the insert (core metal) and the mold in order to prevent leakage of the resin material from the mating surfaces of the mold. In addition, when the resin material leaks from the mating surfaces of the mold, post-processing such as removing excess resin layers generated on the molded product is required.

[0005] An object of the present invention is to provide a method for manufacturing a bush, which does not require strict dimensional accuracy when providing a resin layer on a core metal, and further suppresses generation of excess resin layers that require post-processing. Means for Solving the Problems

[0006] (1) The bushing manufacturing method according to the present invention is a bushing manufacturing method for obtaining a bushing in which an inner member, whose outer circumferential surface of a core metal is covered with a resin layer, is disposed inside an outer cylinder via an elastic layer, and the method includes: a resin cylinder preparation step of preparing a resin cylinder made of resin as the resin layer; a core metal preparation step of preparing the core metal; a core metal heating step of heating the core metal; and a joining step of joining the core metal and the resin cylinder by inserting the core metal after the core metal heating step into the resin cylinder through an opening formed at the axial end of the resin cylinder prepared in the resin cylinder preparation step. According to the bushing manufacturing method according to the present invention, strict dimensional accuracy is not required when providing the resin layer on the core metal, and furthermore, the generation of excess resin layer requiring post-processing is suppressed.

[0007] (2) Preferably, in the method for manufacturing a bush as described in (1) above, the core metal is formed from two core metal parts which are formed into a single core metal by abutting each other on the same axis, the core metal preparation step is a step of preparing the two core metal parts, the core metal heating step is a step of heating each of the two core metal parts, and the joining step is a step of joining the two core metal parts and the resin cylinder by inserting each of the two core metal parts after the heating step into the resin cylinder through an opening formed at the axial end of the resin cylinder until the abutting ends of the two core metal parts abut each other on the same axis. In this case, a bush with high dimensional accuracy can be manufactured.

[0008] (3) In the method for manufacturing a bush described in (2) above, the outer circumferential surface of the core metal is the outer circumferential surface of the core metal component, and it is preferable that the outer circumferential surface of the core metal component includes a tapered surface that tapers radially inward toward the abutment end of the core metal component. In this case, a bush with high durability can be manufactured.

[0009] (4) In any one of the methods for manufacturing a bush described in (1) to (3) above, the core heating step is preferably a step of heating the core by induction heating using a winding wire. In this case, the entire outer surface of the core can be heated simply and easily.

[0010] (5) In any one of the bush manufacturing methods described in (1) to (3) above, it is preferable that the core prepared in the core heating step is a core having irregularities on at least a portion of the outer surface of the core that is covered by the resin layer. In this case, the resin layer can be more firmly fixed to the outer surface of the core.

[0011] (6) In any one of the methods for manufacturing a bush described in (1) to (5) above, the core preparation step preferably includes a roughening step in which the outer surface of the core is roughened, and the irregularities are formed by the roughening step. In this case, the resin layer can be more firmly fixed to the outer surface of the core.

[0012] (7) In the bush manufacturing method described in (6) above, it is preferable to use laser processing for the roughening process. In this case, irregularities can be easily and inexpensively created on the outer surface of the core metal.

[0013] (8) In the method for manufacturing a bush described in (7) above, the elastic layer is an elastic layer bonded to the outer surface of the core metal, and the roughening process is preferably a process of laser processing the outer surface of the core metal that bonds to the elastic layer, as well as the region of the outer surface of the core metal that bonds to the resin cylinder. In this case, irregularities can be easily and simply formed in the region of the elastic layer that bonds to the resin cylinder as well as the region that bonds to the resin cylinder.

[0014] (9) In any one of the methods for manufacturing a bush according to (1) to (8) above, the core preparation step may be a step of preparing a resin cylinder in which the elastic layer and the outer cylinder are integrally bonded to the outer circumference of the resin cylinder. In this case, the bush can be manufactured with the resin layer, elastic layer and outer cylinder already integrally bonded.

[0015] (10) In any one of the above methods for manufacturing a bush, the method may further include an integration step after the bonding step, in which the elastic layer and the outer cylinder are integrally bonded to the outer circumference of the resin cylinder. In this case, the bush can be manufactured by separately bonding the elastic layer and the outer cylinder integrally after the manufacturing of the inner member. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a method for manufacturing bushings that does not require strict dimensional accuracy when providing a resin layer on a core metal, and furthermore, suppresses the generation of excess resin layer that requires post-processing. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic cross-sectional view showing an example of a bush that can be manufactured using the bush manufacturing method of the present invention. [Figure 2] Figure 1 is a schematic cross-sectional view illustrating an example of the operation of the bushing. [Figure 3] This is a cross-sectional view illustrating a method for manufacturing a bush, which is a first embodiment of the present invention. [Figure 4] Figure 3 is a schematic cross-sectional view showing the core metal component. [Figure 5] This cross-sectional view schematically illustrates a phenomenon that may occur when using a core metal component with a straight outer shape. [Figure 6] This is a schematic cross-sectional view showing another example of a bush that can be manufactured using the bush manufacturing method of the present invention. [Figure 7]FIG. 2 is a cross-sectional view schematically illustrating a bushing manufacturing method that is the second embodiment of the present invention. [Figure 8] FIG. 7 is a cross-sectional view schematically showing the core metal component illustrated in FIG. 7. [Figure 9] FIG. 6 is a cross-sectional view schematically showing the inner member illustrated in FIG. 6. [Figure 10] FIG. 7 is a cross-sectional view schematically showing another example of the inner member of the bushing. [Figure 11] FIG. 11 is a cross-sectional view schematically showing an example of a core metal that can be used for insert-molding the inner member illustrated in FIG. 10. DETAILED DESCRIPTION OF EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, several exemplary embodiments of the bushing manufacturing method according to the present invention will be described with reference to the attached drawings.

[0019] FIG. 1 schematically illustrates an example of a bushing that can be manufactured by using the bushing manufacturing method according to the present invention.

[0020] In FIG. 1, reference sign O1 denotes the central axis of the bushing. FIG. 1 schematically shows an exemplary bushing 1A in a cross section including the central axis O1 of the bushing 1A (hereinafter also simply referred to as "axis O1").

[0021] In the present disclosure, the direction in which the axis O1 extends is also referred to as "axial direction". Further, in the present disclosure, the direction orthogonal to the axis O1 is also referred to as "axis-perpendicular direction" or "radial direction". In particular, of the radial direction, the side closer to the axis O1 is also referred to as "radially inner side", and the side farther from the axis O1 is also referred to as "radially outer side". Further, in the present disclosure, the direction extending in the circumferential direction around the axis O1 is also simply referred to as "circumferential direction".

[0022] As shown in Figure 1, the bush has an inner member 4 in which the outer peripheral surface F2 of the core metal 2 is covered by a resin layer 3, and the inner member 4 is positioned inside the outer cylinder 6 via an elastic layer 5. That is, the bush comprises a resin layer 3 that covers the outer peripheral surface (F2) of the inner member 4, an elastic layer 5 positioned on the outer peripheral side of the resin layer 3, and an outer cylinder 6 positioned on the outer peripheral side of the elastic layer 5.

[0023] As shown in Figure 1, the bush 1A comprises a resin layer 3 coupled to the outer circumferential surface F2 of the core metal 2, an elastic layer 5 coupled to the outer circumferential surface F3 of the resin layer 3, and an outer cylinder 6 coupled to the outer circumferential surface F5 of the elastic layer 5. In the bush 1A, the inner member 4 is a cylindrical member (inner cylinder) attached to either the vibration generating side or the vibration receiving side. In the bush 1A, the core metal 2 and the resin layer 3 are formed as a single inner member 4.

[0024] The core metal 2 is a metal core metal. In this disclosure, the core metal 2 is a cylindrical core metal. However, the core metal 2 may be a polygonal cylindrical core metal, as long as it is a cylindrical core metal. Furthermore, the core metal 2 is not limited to a cylindrical core metal. For example, the core metal 2 may be a solid core metal. Examples of metals that form the core metal 2 include aluminum alloys and iron.

[0025] The resin layer 3 is a resin cylinder 13 made of resin. In this disclosure, the resin cylinder 13 is a cylindrical resin cylinder. However, the resin cylinder 13 may be a polygonal cylindrical resin cylinder as long as it is a cylindrical resin cylinder. The resin cylinder 13 is welded to the outer surface F2 of the core metal 2, as described later. The resin used to form the resin cylinder 13 is a resin whose melting temperature is within a predetermined temperature range (for example, 120°C to 176°C), and is preferably a resin with high abrasion resistance and chemical resistance. An example of the resin used to form the resin cylinder 13 is polyamide (including glass fiber reinforcement).

[0026] In the bush 1A, the resin layer 3 comprises a bulge-shaped portion 31 and two shaft portions 32 connected to the bulge-shaped portion 31. In this embodiment, the bulge-shaped portion 31 and the two shaft portions 32 are integrally formed. Here, the bulge shape refers to a shape in which a part of the outer surface of the resin layer 3 is locally bulged in a spherical shape. As shown in Figure 1, in the bush 1A, the bulge-shaped portion 31 is positioned in the axial direction with respect to the axial center P1 of the bush 1A. However, the bulge-shaped portion 31 can be positioned so as to be off-center to one of the two axial ends 1e of the bush 1A rather than the axial center P1 of the bush 1A. Also, here, the axial center P1 of the bush 1A is assumed to coincide with the axial center of the inner member 4 (core metal 2).

[0027] The elastic layer 5 has a cylindrical shape formed from an elastic material. In this disclosure, the elastic layer 5 has a cylindrical shape. However, the elastic layer 5 may have a polygonal cylindrical shape as long as it is cylindrical. Examples of the elastic material forming the elastic layer 5 include rubber.

[0028] In bush 1A, the elastic layer 5 comprises a covering portion 51 that covers the bulge-shaped portion 31 of the resin layer 3, and two support portions 52 connected to the covering portion 51. In bush 1A, the covering portion 51 and the two support portions 52 are integrally formed. The covering portion 51 is an annular covering portion that extends annularly in the circumferential direction around the axis O1. The two support portions 52 are also annular support portions that extend annularly in the circumferential direction around the axis O1. Furthermore, in bush 1A, an annular joint portion 7 is formed between the support portion 52 of the elastic layer 5 and the shaft portion 32 of the resin layer 3, connecting the support portion 52 and the shaft portion 32. The annular joint portion 7 extends annularly in the circumferential direction around the axis O1. On the other hand, an annular non-connecting portion 8 is formed between the covering portion 51 of the elastic layer 5 and the bulge-shaped portion 31 of the resin layer 3, preventing the covering portion 51 and the bulge-shaped portion 31 from being joined. The annular non-connecting portion 8 also extends annularly in the circumferential direction around the axis O1. The annular non-connecting portion 8 is an annular sealed gap formed between the covering portion 51 of the elastic layer 5 and the bulge-shaped portion 31 of the resin layer 3, closed by two annular connecting portions 7. In the bush 1A, the annular non-connecting portion 8 is filled with lubricating fluid 11.

[0029] The outer cylinder 6 is a cylindrical member attached to either the vibration generating side or the vibration receiving side. The outer cylinder 6 is bonded to the outer circumferential surface of the elastic layer 5. The inner member 4 and the outer cylinder 6 are mainly supported by the support portion 52 of the elastic layer 5. In addition, in the bush 1A, the bulge-shaped portion 31 of the resin layer 3 is supported by the covering portion 51 of the elastic layer 5 and the lubricating fluid 11.

[0030] The outer cylinder 6 is a metal outer cylinder. The outer cylinder 6 is bonded to the outer circumferential surface F5 of the elastic layer 5. In this disclosure, the outer cylinder 6 is a cylindrical outer cylinder. However, the outer cylinder 6 may be a polygonal cylindrical outer cylinder as long as it is cylindrical. Examples of metals that form the outer cylinder 6 include aluminum alloy and iron. The outer cylinder 6 may also be a resin outer cylinder.

[0031] Figure 2 schematically shows an example of the operation of bushing 1A, corresponding to the cross-section in Figure 1. In the following explanation, bushing 1A will be described as being used in a vehicle suspension system.

[0032] As shown in Figure 2, the outer cylinder 6 is fixed to the suspension arm 100 by fitting it inside the fixing sleeve 101 provided on the suspension arm 100. In contrast, the inner member 4 is fixed to the vehicle body (not shown) via fastening elements such as bolts and nuts, for example, by passing fastening elements such as bolts and nuts through the through holes A1 formed inside the inner member 4. However, the bush 1A can also fix the outer cylinder 6 to the fixing sleeve 101 provided on the vehicle body while simultaneously fixing the inner member 4 to the suspension arm 100 via fastening elements such as bolts and nuts.

[0033] The bush 1A can absorb the twisting of the inner member 4 against the outer cylinder 6. Figure 2 illustrates a state in which the inner member 4 is twisting inside the outer cylinder 6 via the elastic layer 5.

[0034] When bushing 1A is used in a suspension device, three-dimensional input from the inner member 4 may cause, for example, twisting or bending inside bushing 1A. Here, "twisting" refers to the relative movement (relative rotation) of the inner member 4 and the outer cylinder 6 around the axis O1 at an angle θ1 in the circumferential direction. "Bending" refers to the relative movement (relative rotation) of at least one of the inner member 4 and the outer cylinder 6 around the axis O1 at an angle θ1 in the circumferential direction while being inclined with respect to the axis O1 at an angle α1, as shown in Figure 2. However, in this disclosure, "bending" includes movement that is inclined with respect to the axis O1 without at least one of the inner member 4 and the outer cylinder 6 moving relative to the axis O1 in the circumferential direction, as shown in Figure 2.

[0035] As shown in Figure 2, when an input is applied that causes twisting in the bush 1A, the elastic layer 5 and the inner member 4 are displaced relative to each other in the region of the unconnected portion 8, causing them to separate. This allows the bush 1A to absorb the twisting of the inner member 4 relative to the outer cylinder 6 while maintaining vibration damping performance. In the bush 1A, the lubricating fluid 11 is filled inside the annular connected portion 8, which allows for smoother absorption of the twisting of the inner member 4 relative to the outer cylinder 6. However, the lubricating fluid 11 can be omitted.

[0036] As a method for manufacturing the bush 1A, for example, a conventional technique known as insert molding is used, in which a resin layer 3 is injection molded using a core metal 2 as an insert.

[0037] However, in molding using molds, it is necessary to improve the dimensional accuracy of both the insert (core) and the mold in order to prevent leakage of resin material from the mold mating surface. In addition, if resin material leaks from the mold mating surface, post-processing such as removing the excess resin layer that has formed on the molded product is required.

[0038] In contrast, Figure 3 schematically shows a method for manufacturing a bush, which is a first embodiment of the present invention and does not require the use of a mold during the manufacturing of the inner member 4. In this embodiment, the bush 1A can be obtained by a method that includes the following steps.

[0039] The manufacturing method of the bush in this embodiment includes a resin cylinder preparation step of preparing a resin cylinder 13 made of resin as the resin layer 3, a core metal preparation step of preparing a core metal 2, a core metal heating step of heating the core metal 2, and a joining step of joining the core metal 2 and the resin cylinder 13 by inserting the core metal 2 after the core metal heating step into the resin cylinder 13 through an opening A13 formed at the axial end 13a of the resin cylinder 13 prepared in the resin cylinder preparation step.

[0040] In the resin cylinder preparation step described above, the resin cylinder 13 is prepared. As shown in Figure 3, in this embodiment, the inner circumferential surface F32 of the resin cylinder 13 is formed by two tapered surfaces F321. Specifically, as shown in Figure 3, the tapered surface F321 is a tapered surface that tapers radially inward from the opening A13 formed at the axial end 13a of the resin cylinder 13 toward the axial center (P1) of the resin cylinder 13. In this embodiment, the tapered surface F321 is formed to correspond to the tapered surface F121 of the core metal component 12, which will be described later.

[0041] In the core preparation step, a core 2 is prepared. In the bush manufacturing method of this embodiment, two core components 12 are prepared in the core preparation step. More specifically, in this embodiment, the core 2 is formed by two core components 12 which are formed into one core 2 by abutting each other on the same axis O1.

[0042] Figure 4 schematically shows the core metal component 12 shown in Figure 1 in a cross-section including the axis O1.

[0043] In bush 1A, the outer circumferential surface F2 of the core metal 2 is the outer circumferential surface F12 of the two core metal parts 12. The outer circumferential surface F12 of the core metal part 12 includes a tapered surface F121 that tapers radially inward toward the abutment end 12a of the core metal part 12. In this embodiment, the acute angle α2 of the angle that the tapered surface F121 makes with respect to the axis O1 is 2 degrees. However, the angle α2 does not need to include 0 degrees. For example, the angle α2 can be 2 degrees or more. In bush 1A, the central axis of the core metal 2 (core metal part 12) is assumed to coincide with the axis O1.

[0044] As shown in Figure 1, in bush 1A, the two core metal parts 12 have the same shape. As a result, in bush 1A, the abutting position of the two core metal parts 12 is located at the axial center P1 of bush 1A, as shown in Figure 1. By setting the abutting position of the two core metal parts 12 to the axial center P1 of bush 1A, it is possible to standardize the parts of the core metal parts 12 that form the core metal 2, as in bush 1A.

[0045] However, the shapes of the two core metal parts 12 can be different. For example, the axial length of one of the two core metal parts 12 can be different from the axial length of the other core metal part 12. If the axial length of one of the two core metal parts 12 is different from the axial length of the other core metal part 12, for example, the abutment position of the two core metal parts 12 can be shifted from the axial center P1 of the bush 1A to one of the two axial ends 1e of the bush 1A.

[0046] The core heating step is a step of heating the core 2. In this embodiment, the core heating step is a step of heating each of the two core components 12.

[0047] Referring to Figure 3, the two core metal components 12 can each be heated using various heating methods. In this embodiment, the two core metal components 12 are each heated by induction heating using the winding 10, as described later. The heating temperature of the core metal components 12 is set to be above the temperature at which the resin cylinder 13 melts. Furthermore, the heating temperature of the core metal components 12 is kept below a temperature that does not deform the resin cylinder 13, for example, a temperature that does not deform the shaft portion 32 of the resin cylinder 13. Preferably, the heating temperature of the core metal components 12 is set such that when the heated core metal component 12 is pressed against the inner surface of the resin cylinder 13, only the surface layer of the inner surface of the resin cylinder 13 melts.

[0048] In the aforementioned joining step, the core metal 2 and the resin cylinder 13 are joined by inserting the core metal 2 into the resin cylinder 13 through the opening A13 formed at the axial end 13a of the resin cylinder 13. As shown in Figure 3, in this embodiment, the joining step joins the two core metal parts 12 and the resin cylinder 13 by inserting each of the two core metal parts 12 after the heating step into the resin cylinder 13 through the opening A13 formed at the axial end 13a of the resin cylinder 13 until the abutting ends 12a of the two core metal parts 12 abut each other on the same axis O1. As a result, the two core metal parts 12 become integrated with the resin cylinder 13 as the core metal parts 12 cool.

[0049] According to the bush manufacturing method of this embodiment, the core metal 2 and the resin cylinder 13 can be joined by inserting the core metal 2 into the opening A13 formed at the axial end 13a of the resin cylinder 13. Therefore, according to the bush manufacturing method of this embodiment, the inner member 4 can be manufactured simply by inserting the heated core metal 2 into the resin cylinder 13. Furthermore, according to the bush manufacturing method of this embodiment, the inner member 4 can be manufactured without using a mold, thus suppressing the generation of excess resin layer that requires post-processing.

[0050] Therefore, according to the bushing manufacturing method of this embodiment, strict dimensional accuracy is not required when providing the resin layer 3 to the core metal 2, and furthermore, the generation of excess resin layer requiring post-processing is suppressed.

[0051] Incidentally, according to the bush manufacturing method of the present invention, the core metal 2 is a single core metal, and the single core metal 2 and the resin cylinder 13 can be joined by inserting the single core metal 2 into only one opening A13 formed at the axial end 13a of the resin cylinder 13.

[0052] However, if a single core metal 2 is inserted only into one opening A13 formed at the axial end 13a of the resin cylinder 13, there is a risk of deformation occurring in the resin cylinder 13.

[0053] In contrast, as in the bushing manufacturing method of this embodiment, by using two core metal parts 12, when the abutting ends 12a of the two core metal parts 12 are inserted into the resin cylinder 13 from the opening A13 formed at the axial end 13a of the resin cylinder 13 until they abut each other on the same axis O1, the resin cylinder 13 is less likely to suffer deformation. Therefore, when using two core metal parts 12 as in the bushing manufacturing method of this embodiment, a bushing 1A with high dimensional accuracy can be manufactured.

[0054] Furthermore, as shown in Figure 3, in the bush manufacturing method of this embodiment, the core preparation step is a step of preparing a resin cylinder 13 in which an elastic layer 5 and an outer cylinder 6 are integrally bonded to the outer circumference of the resin cylinder 13. The resin cylinder 13 in which the elastic layer 5 and the outer cylinder 6 are integrally bonded can be molded, for example, by placing the resin cylinder 13 and the outer cylinder 6 as inserts inside a mold and injecting an elastic material into the inside of the mold.

[0055] In the core preparation step, if a resin cylinder 13 is prepared in which the elastic layer 5 and the outer cylinder 6 are integrally bonded to the outer circumference of the resin cylinder 13, the bush 1A can be manufactured with the resin layer 3, elastic layer 5 and outer cylinder 6 already integrally bonded. Alternatively, if a resin cylinder 13 is prepared in which the elastic layer 5 and the outer cylinder 6 are integrally bonded, as shown in Figure 3, the resin cylinder preparation step and the core preparation step can be performed at the same time.

[0056] Incidentally, according to the bush manufacturing method of the present invention, the outer shape of the core metal component 12 can be a straight shape parallel to the axis O1. That is, the outer circumferential surface F12 of the core metal component 12 can have the same diameter in the axial direction.

[0057] Figure 5 schematically shows the phenomena that may occur when a core metal component 12 with a straight outer shape is used as the core metal component 12 in the bush manufacturing method of this embodiment.

[0058] According to the bushing manufacturing method of the present invention, the resin cylinder 13 is melted by the heat emitted from the core metal component 12. On the other hand, as shown in Figure 5, if the outer peripheral surface F12 of the core metal component 12 is a straight surface F122 that extends straight parallel to the axis O1, when the core metal component 12 is pushed in, the abutting end 12a of the core metal component 12 may scrape and push in the molten portion 13p of the resin cylinder 13, as shown in Figure 5.

[0059] When the abutting ends 12a of the two core metal parts 12 each scrape out the molten portion 13p of the resin cylinder 13 and push it into the inside of the resin cylinder 13, it is conceivable that the molten portion 13p of the resin cylinder 13 may become stuck between the abutting ends 12a of the two core metal parts 12, as shown in Figure 5.

[0060] If the molten portion 13p of the resin cylinder 13 gets stuck between the abutting ends 12a of the two core metal parts 12, the abutting ends 12a of the two core metal parts 12 will not come into complete contact, and a gap will be created between the abutting ends 12a of the two core metal parts 12.

[0061] If a gap occurs between the abutment ends 12a of the two core metal parts 12, the space between the abutment ends 12a of the two core metal parts 12, which constitutes the inner member 4, will be supported only by the resin layer 3, or, looking at the bush 1A as a whole, only by the resin layer 3, the elastic layer 5, and the outer cylinder 6. In this case, the bush may experience sagging (permanent deformation) between the abutment ends 12a of the two core metal parts 12 over time.

[0062] In contrast, in the bush manufacturing method of this embodiment, the outer circumferential surface F12 of the core metal component 12, specifically the tip portion on the abutment end 12a side, is formed by a tapered surface F121 that tapers radially inward toward the abutment end 12a, as shown in Figure 3. In this case, the molten portion 13p of the resin cylinder 13, melted by the heat emitted from the core metal component 12, can be released along the tapered surface F121 of the core metal component 12 to the side opposite to the pushing side of the core metal component 12. This suppresses the occurrence of the phenomenon where the molten portion 13p of the resin cylinder 13 gets stuck between the abutment ends 12a of the two core metal components 12. Therefore, by making the tip portion on the abutment end 12a side of the outer circumferential surface F12 of the core metal component 12 a tapered surface F121, a highly durable bush 1A can be manufactured.

[0063] By the way, in the bush manufacturing method according to the present invention, there are no particular limitations on the method of heating the core metal component 12 (core metal 2). The core metal component 12 (core metal 2) can be heated, for example, by a heater or a heating furnace.

[0064] In contrast, as shown in Figure 3, in the bush manufacturing method of this embodiment, the core metal heating step is a step of heating the core metal component 12 by induction heating using the winding wire 10.

[0065] In this embodiment, the core metal component 12 is heated by being placed inside the winding 10. The winding 10 can be, for example, a conductive wire, specifically a metal wire. According to the bush manufacturing method of this embodiment, the core metal component 12 generates heat due to the electrical resistance of the core metal component 12 when electricity is passed through the winding 10. As a result, the core metal component 12 is heated in accordance with the time the winding 10 is energized while it is placed inside the winding 10. Therefore, by using induction heating to heat the core metal component 12, the entire outer surface F12 of the core metal component 12 can be heated simply and easily.

[0066] In particular, in this embodiment, the winding 10 is arranged on the same axis O1 as the resin cylinder 13. By arranging the resin cylinder 13 and the winding 10 on the same axis O1 in this way, the core metal component 12 heated inside the winding 10 can be directly inserted into the resin cylinder 13 through the opening A13 formed at the axial end 13a of the resin cylinder 13, as shown by the arrow in Figure 3. In this case, for example, the heated core metal component 12 can be automatically pushed into the resin cylinder 13 using an automated machine. Therefore, heating the core metal component 12 by induction heating can improve the work efficiency during the manufacturing of the bush 1A.

[0067] By the way, in the bush manufacturing method of this embodiment, the core metal part 12 has irregularities on at least a portion of the outer peripheral surface F12 of the core metal part 12 that is covered by the resin layer 3.

[0068] Referring to Figure 4, in this embodiment, the irregularities are formed in the shaded area indicated by reference numeral 12b. In this embodiment, the irregularities are formed on the tapered surface F121.

[0069] If at least a portion of the outer circumferential surface F12 of the core metal component 12 that is covered by the resin layer 3 has irregularities, the resin cylinder 13, which is melted by the heat of the core metal component 12, will bite into the irregularities on the outer circumferential surface F12 of the core metal component 12 (by a so-called anchoring effect), thereby firmly bonding to the outer circumferential surface F12 of the core metal component 12. Therefore, if irregularities are formed on at least a portion of the area of ​​the outer circumferential surface F12 of the core metal component 12 to which the resin layer 3 is bonded, the resin layer 3 can be fixed more firmly to the outer circumferential surface F12 of the core metal component 12.

[0070] Furthermore, the irregularities formed on the outer surface F12 of the core metal component 12 only need to be minute irregularities that allow the molten resin material to fill the gaps between the irregularities, thereby creating a so-called anchoring effect after the resin material hardens. For this reason, for example, if the core metal component 12 is formed by casting, it may be possible to use the core metal component 12 as is.

[0071] On the other hand, in the bush manufacturing method of this embodiment, the core metal preparation step includes a roughening step in which the outer circumferential surface F2 of the core metal 2 is roughened, and the irregularities are formed by the roughening step.

[0072] If the outer surface F2 of the core metal 2 is a smooth surface, it may be difficult to obtain an anchoring effect. In this case, it is necessary to increase the bonding force between the outer surface F2 of the core metal 2 and the resin layer 3. Therefore, in the bush manufacturing method of this embodiment, roughening is actively performed on the outer surface F2 of the core metal 2 before the core metal heating step in which the core metal 2 is heated. As in this embodiment, if roughening is performed on the outer surface F2 of the core metal 2 before the core metal heating step, the resin layer 3 can be more firmly fixed to the outer surface F2 of the core metal 2. In this embodiment, as shown in Figure 3, roughening is performed on the outer surface F12 of the core metal component 12 before the core metal component 12 is placed inside the winding 10.

[0073] For example, laser processing, cutting, blasting, and chemical treatment can be used as the surface roughening processes. However, the above surface processing is merely illustrative. Therefore, methods other than those described above can be used to form the irregularities on the outer surface F12 of the core metal part 12 (the outer surface F2 of the core metal 2).

[0074] In the bush manufacturing method of this embodiment, laser processing is used for the roughening process. When using laser processing, it is possible to easily and inexpensively create minute irregularities on the outer surface F12 of the core metal part 12 (outer surface F2 of the core metal 2) that can exert an anchoring effect on the molten resin material, compared to when using cutting or the like.

[0075] Referring to Figure 1, the region where the roughening process is performed, that is, the region 12b where the irregularities are formed, is the entire region of the outer circumferential surface F12 of the core metal part 12 that connects with the resin cylinder 13. However, region 12b only needs to be formed in at least a part of the region that connects with the resin cylinder 13. Also, in this embodiment, region 12b is formed circumferentially around the axis O1 over the entire circumference. However, region 12b may be formed intermittently or locally in only one location circumferentially around the axis O1.

[0076] By the way, in bush 1A, the elastic layer 5 is bonded to the outer surface F13 of the resin layer 3, but it can also be bonded to the outer surface F2 of the core metal 2.

[0077] Figure 6 schematically shows another example of a bush that can be manufactured using the bush manufacturing method of the present invention.

[0078] In Figure 6, reference numeral 1B denotes a bush as another example that can be manufactured using the bush manufacturing method. In bush 1B, the elastic layer 5 is an elastic layer bonded to the outer circumferential surface F2 of the core metal 2. In this example, the resin cylinder 13 constitutes only the bulge-shaped portion 31.

[0079] As shown in Figure 6, in bush 1B, the resin layer 3 is bonded to the tapered surface F121 of the outer circumferential surface F12 of the core metal component 12 (outer circumferential surface F2 of the core metal 2). The aforementioned irregularities are formed on the tapered surface F121. In this example, the region 12b1 in which the irregularities are formed coincides with the region where the tapered surface F121 exists. However, region 12b1 only needs to be at least a part of the tapered surface F121, as described above. Also in bush 1B, the elastic layer 5 is bonded to the straight surface F122 of the outer circumferential surface F12 of the core metal component 12 (outer circumferential surface F2 of the core metal 2). In this example, the region 12b2 in which the irregularities are formed coincides with the region of the straight surface F122 that is bonded to the elastic layer 5. However, region 12b2 also only needs to be at least a part of the region of the bonded area with the elastic layer 5, as described above.

[0080] Figure 7 is a cross-sectional view illustrating a second embodiment of the present invention, which is a method for manufacturing a bush. Here, a method for manufacturing bush 1B will be described.

[0081] As shown in Figure 7, in the bush manufacturing method of this embodiment, the core metal 2 is formed by two core metal parts 12 that are abutted against each other on the same axis O1 to form a single core metal 2. In this embodiment, the outer circumferential surface F12 of the core metal part 12 is formed by a tapered surface F121 and a straight surface F122. Also in this embodiment, the inner circumferential surface F32 of the resin cylinder 13 is formed by two tapered surfaces F321.

[0082] The bush manufacturing method of this embodiment includes basically the same steps as the bush manufacturing method of the first embodiment. That is, the bush manufacturing method of this embodiment includes the resin cylinder preparation step, the core metal preparation step, the core metal heating step, and the joining step. In addition, in this embodiment, the core metal preparation step includes the roughening step.

[0083] However, in the bush manufacturing method of this embodiment, the roughening process is a process of performing laser processing on the outer surface F2 of the core metal 2, including the region that connects with the resin cylinder 13 and the region that connects with the elastic layer 5. In this embodiment, the roughening process is a process of performing laser processing on the outer surface F12 of the core metal part 12, including the region that connects with the resin cylinder 13 and the region that connects with the elastic layer 5.

[0084] Figure 8 shows a schematic representation of the core metal component 12 shown in Figure 7.

[0085] When bonding the elastic layer 5 to the outer circumferential surface F12 of the core metal part 12 together with the resin layer 3, the roughening process involves laser processing on both the region that bonds with the resin cylinder 13 (tapered surface F121 in this embodiment) and the region that bonds with the elastic layer 5 (straight surface F122 in this embodiment). Laser processing allows for adjustment of individual roughness levels by changing the laser output. Therefore, by using laser processing for roughening the outer circumferential surface F12 of the core metal part 12, as shown in Figure 8, the region that bonds with the resin cylinder 13 can be made into the region 12b1 where the irregularities are formed, and the region that bonds with the elastic layer 5 can be made into the region 12b2 where the irregularities are formed. Therefore, as in this embodiment, by performing laser processing on the outer surface F12 of the core metal part 12, both in the region that connects with the resin cylinder 13 and the region that connects with the elastic layer 5, the roughness of the region that connects with the resin cylinder 13 and the region that connects with the elastic layer 5 can be easily and simply formed in a series of steps.

[0086] Therefore, as in this embodiment, if laser processing is performed on the outer surface F12 of the core metal component 12, both in the region that connects with the resin cylinder 13 and the region that connects with the elastic layer 5, then by performing the laser processing in one step, i.e., a single laser processing, it is possible to easily and simply form irregularities in both the region that connects with the resin cylinder 13 and the region that connects with the elastic layer 5. In Figure 7, the core metal component 12 is shown in a state where it is placed inside the induction heating winding 10 after the roughening process.

[0087] Furthermore, the manufacturing method of the bush in this embodiment further includes an integration step after the bonding step, in which the elastic layer 5 and the outer cylinder 6 are integrally bonded to the outer circumference of the resin cylinder 13.

[0088] Figure 9 schematically shows the inner member 4 shown in Figure 6 after the bonding process.

[0089] In the aforementioned integration process, the inner member 4 shown in Figure 9 is used as a core metal 2 covered with a resin layer 3. The inner member 4 and the outer cylinder 6 are placed inside the mold as insert parts, and an elastic material is injected into the mold. As shown in Figure 6, the inner member 4, the elastic layer 5, and the outer cylinder 6 can be integrally molded.

[0090] As in the bush manufacturing method of this embodiment, if the integration step is performed after the bonding step, the bush can be manufactured by separately bonding the elastic layer 5 and the outer cylinder 6 together after the manufacturing of the inner member 4.

[0091] By the way, as explained above, when bonding the elastic layer 5 to the outer surface F13 of the resin layer 3, the roughening process can be a process of performing laser processing on the outer surface F2 of the core metal 2, both in the region that bonds with the resin layer 3 and the region that bonds with the elastic layer 5. In this case, the core metal 2 equipped with the resin layer 3 as the inner member 4 can be molded as an insert product.

[0092] Figure 10 schematically shows yet another example of the inner member 4 of the bush. Figure 11 schematically shows an example of a mandrel that can be used for insert molding the inner member 4 shown in Figure 10.

[0093] In the inner member 4 of Figure 10, the core metal 2 is a single core metal whose outer surface F2 has a straight shape parallel to the axis O1. When the elastic layer 5 is firmly bonded to the outer surface F2 of this core metal 2 together with the resin layer 3, laser processing can be performed on the outer surface F2 of the core metal 2 to create roughness, in both the region bonded to the resin layer 3 and the region bonded to the elastic layer 5. As a result, as shown in Figure 11, the region bonded to the resin layer 3 can be made into the region 12b1 where the roughness is formed, and the region bonded to the elastic layer 5 can be made into the region 12b2 where the roughness is formed. As mentioned earlier, with laser processing, the roughness of the region bonded to the resin layer 3 and the region bonded to the elastic layer 5 can be easily and simply adjusted by changing the laser output.

[0094] Furthermore, when using the core metal 2 shown in Figure 10, the inner member 4 shown in Figure 11 can be manufactured by insert molding. The inner member 4 shown in Figure 10 can be integrally molded by placing the core metal 2 shown in Figure 11 as an insert inside the mold after the roughening process, and injecting resin material into the mold, thereby forming the core metal 2 covered with the resin layer 3, i.e., the inner member 4. In this case, the inner member 4 can be manufactured by separately joining the core metal 2 and the resin layer 3 together after the roughening process of the core metal 2.

[0095] Furthermore, in Figure 10, the inner member 4 and the outer cylinder 6 can be placed inside the mold as insert parts, and the elastic layer 5 and the outer cylinder 6 can be integrally molded by injecting an elastic material into the inside of the mold.

[0096] The above describes only exemplary embodiments of the bush manufacturing method according to the present invention, and various modifications are possible according to the claims. For example, since all of the bushes described above are fastened in the axial direction of the bush, the abutment ends 12a of the two core metal parts 12 can be fixed to each other only by abutting. However, the abutment ends 12a of the two core metal parts 12 may be bonded together. Also, although the resin layer 3 was described as a resin layer having a bulge shape, the shape of the resin layer 3 is not limited to having a bulge shape. Furthermore, although the bush obtained by the bush manufacturing method according to the present invention was described as a bush for a suspension device, the bush is not limited to a bush for a suspension device as long as three-dimensional input is applied to at least one of the inner member 4 and the outer cylinder 6. [Explanation of Symbols]

[0097] 1A: Bushing, 1B: Bushing, 1e: Axial end of bushing, 2: Core, 12: Core component, 12a: Butt end of core component, 3: Resin layer, 13: Resin cylinder, 13a: Axial end of resin cylinder, 31: Bulge-shaped part of resin layer, 32: Shaft part of resin layer, 4: Inner member, 5: Elastic layer, 51: Covering part of elastic layer, 52: Support part of elastic layer, 6: Outer cylinder, 7: Annular joint, 8: Annular non-joint part, 11: Lubricating fluid, 100: Suspension arm, 101: Fixing sleeve provided on suspension arm, A13: Opening formed at the axial end of resin cylinder, F2: Outer surface of core, F12: Outer surface of core component, F121: Tapered surface of outer surface of core component, F122: Straight surface of outer surface of core component, F32: Inner surface of the resin cylinder, F321: Tapered surface of the inner surface of the resin cylinder, O1: Axis (central axis of the bush), P1: Center of the bush in the axial direction

Claims

1. A method for manufacturing a bushing, for obtaining a bushing in which an inner member, whose outer surface of a core metal is covered with a resin layer, is disposed inside an outer cylinder via an elastic layer, The resin layer is prepared in the form of a resin cylinder preparation step, The process of preparing the core metal, A core heating step, in which the core metal is heated, A method for manufacturing a bush, comprising a joining step of joining the core metal after the core metal heating step to the resin cylinder prepared in the resin cylinder preparation step by inserting the core metal into the resin cylinder through an opening formed at the axial end of the resin cylinder prepared in the resin cylinder preparation step.

2. The aforementioned core metal is formed from two core metal components that are abutted against each other on the same axis to form a single core metal. The core preparation step is a step of preparing the two core components, The core heating step is a step of heating each of the two core components, The method for manufacturing a bush according to claim 1, wherein the bonding step is a step of bonding the two core metal parts and the resin cylinder by inserting each of the two core metal parts after the heating step into the resin cylinder through an opening formed at the axial end of the resin cylinder until the abutting ends of the two core metal parts abut each other on the same axis.

3. A method for manufacturing a bush according to claim 2, wherein the outer circumferential surface of the core metal is the outer circumferential surface of the core metal component, and further, the outer circumferential surface of the core metal component includes a tapered surface that tapers radially inward toward the abutment end of the core metal component.

4. The method for manufacturing a bush according to claim 1, wherein the core heating step is a step of heating the core by induction heating using a winding wire.

5. The method for manufacturing a bush according to claim 1, wherein the core prepared in the core heating step is a core having irregularities on at least a portion of the outer surface of the core that is covered by the resin layer.

6. The method for manufacturing a bush according to claim 5, wherein the core preparation step includes a roughening step of roughening the outer surface of the core, and the irregularities are formed by the roughening step.

7. A method for manufacturing a bush according to claim 6, wherein laser processing is used for the roughening process.

8. The elastic layer is an elastic layer bonded to the outer surface of the core metal, The method for manufacturing a bush according to claim 6, wherein the roughening process is a process of performing laser processing on the outer surface of the core metal, including the region that bonds with the resin cylinder and the region that bonds with the elastic layer.

9. The method for manufacturing a bush according to claim 1, wherein the core preparation step is a step of preparing a resin cylinder in which the elastic layer and the outer cylinder are integrally bonded to the outer circumference of the resin cylinder.

10. A method for manufacturing a bush according to claim 1, further comprising an integration step of integrally bonding the elastic layer and the outer cylinder to the outer circumference of the resin cylinder after the bonding step.

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